Automatic telephone system



w. T. POWELL AUTOMATIC TELEPHONE SYSTEM April 6, 192s.

Filed May e. 1921 3 Sheets-Sheel'l l .IOZW ur... wDlOumw INVENTORwww-RED T POWELL ATTORNEY April 6, 1926.

W. T. POWELL AUTOMATIC TELEPHONE SYSTEM Filed May 6. 1921 5 Sheets-Sheet2 INVENTOR WINFBED 'n POWELL ATTO NEY A ril 6 1926.

p w. T. POWELL AUTOMATIC TELEPHONE SYSTEM Filed May 6. 1921 3Sheets-Sheet I5 INVENTOR WIHFRED T. POWELL Patented pr. 6, 1926.:

` UNITED STATES,

PATENT orner..

WINTRED T. POWELL, or ROCHESTER, NEW Yonx, ynssieivon To THESTnoiviBEnG- CARLSON TELEPHONE MANUFACTURING COMPANY, F ROCHESTER, NEWYORK, Ai*

CORPORATION oF NEW YORK.

AUToMATIc TELEPHQNE SYSTEM.

Application led May 6,

To all 107mm t may concern.'

Be it known that I, VVINFRED T. POWELL,

l a citizen of the United States, residing at Rochester, in the countyof Monroe and State of New York, have invented certain new and usefulImprovements infAutoniatic Telephone Systems, of which the following isa full, clear, concise, and exact description.

This invention relates to telephone systems and more particularly totelephone systems employing automatic switches in establishing.telephone connections.

numerical switch was employed to connect a linejor trunk to a trunk, itwas'necessary to provide a separate switch for each of said lines ortrunks. This arrangement, While eliicie'nt in operation, is necessarilyexpensive because of the number of switches employed. v

' sented two separate line switches which are known as secondary lineswitches and function to further extend calling lines to idle Anumericalswitches. At the extreme right of this ligure, there is indicated aconnector switch anda wanted, Sub-station.-

Iii Figure 2 .the invention isapplied to what is commonly known as acall distributing system. At the left of the dotted line of Figure 2thereA appears two incoming trunks which terminate` atY one end in thebrushes of a Single primary line switch. The other end of each of thesetrunks terininates at a distant oiiice through which a calling line maybe extended by automatic switches orby operators cord circuits atoperators positions located thereat.V In the center of Figure 2 thereappears two secondary line switches which function to extend a trunkcircuit Selected by the primary line. switch to an idleiiuineii'calswitch which may be either a selector switch ory a connector switchdepending on the sizeof v indicated. `In former telephone systems wherea noni921'. semina. 467,476.

a wanted sub- .G0 'Figure 3 represents a modified form ot the inventionshown in Fig. 1 and discloses' primary and secondary line switches,while at the extreme right of this figure an abbreviated disclosure ofthe connector switch is 'The line switches used iii this system may beof a structuresubstantially similar tov that disclosed in the patent toClement 1,107,153 patented August 11, 1,914, while the mentionedselector and connector switcliesfniay be substantially similar to thosedisclosed in Patents 815,321aiid 815,176

A granted toKeith, Erickson andI-rickson on March13,1`906 `The linerelayL.y It. and the n cut-cli' relays C. O. are arranged to be inteinr`locking as disclosed'in the patent to Lamb 1,193,160 granted August 1,`1916. l

Uien this invention is yused in a system of the character disclosed inFigure 1 that is a ro-called full automatic telephone sys-` tem, thesubscribers telephone lines may be is provided and therewill thereforebe provided primary line switches for each group ctl00v linesf Eachprimary line For the kuse of eachv lswitch `will have access to 2Osecondaryline switciies and these in turn will haveaccess to 10numerical switches. These numericalv` switches may be first selectorsii, the system is large in size or connector switches iii'the system isrelatively small.y It will be understood that the invention is notlimited to this arrangement or to rthe number of lines or trunksindividual to: a primary line switch. f y

It is` believed that the invention will best be understood by describingthe method ot establishing a telephone connectionlrom a ca-llingsub-station'atiiyto a wanted station indicated at B. .Vhen the callingsubscriber at A. removesk his receiver :troni its switch hook,aciicuitfis" vclosed for the line relay V42 extending from groundedbattery, winding ot .this yline relay, inner, upper back Contact ,andarmature otthe cut-soif relay 3 over the lower side of the callingsubscribers line and through .the sub-statien circuits in series of thecalling'sub-fstation, over .the uppery side of the calling line,uppermost armature and back contact of the cut-ott relay 3 to ground.The line Arelay 2 is energized in this circuit and closes an operatingcircuit for the motor mag-net 4 of the line switch Whichcircuit extendsfrom grounded battery, Winding of the motor magnet, its armature andback contact, outermost front Contact and armature of the line relay 2'inner loire' back contact and armature ot the cut-oit relay 3 through`the test brush 5 and test terminals such as 6 of busy trunks to groundat the iii'ont contact .andi armature of Slo-u7 'releasingrelays such as7. The motor magnet 4. thus advances the brushes 5, 8, y9, 10, '11, and12 i-n -a rotary direction vuntil:thetet'brush 5 engages a testtermi-nail which is characterized by the absence vot potential whichindicates that the vtrunk which is indiyidualto this test terminal isidle.

Let it be assumed that the first idle trunk circuit tested by theprimary line yswitch is that indicated i-n'iigure 1 yat, which time when4the test brush `5 engages the test terni'inal 13 there will be noguarding potential on this test terminal due to the fact that relay 7and relay 11i are not operated.

As a result of this condition, and since the line relay 2 hasremoved'the obstruct-ion from the path of the armature of the cutotli'elay 3 it will be fully operated cin a circuit extending from ground,through its upperwinding, inner front contact and armature of the linerelay 2 back contact, armature and winding ottheniotor magnet et, togrounded battery. The cut-ott relay 3 thus attracts its'armature and atits upper armatures opens the operating circuit of the line rela-y 2,but this relay is of the Vtype that is slew in releasing its armaturesand therefore remains operated for a relatirely short interval. liet theupper armatures and liront contacts of the cut-oit relay 3, the callingrline is extended through the brushes S and 9 ot the primary line.lswitch" to the select trunk circuit hy which acircuit is closed forenergizing the slow releasing relay 7 from grounded battery Which iscompleter through both sides in series Aof the extended -connectionincluding the calling line and trunk terminating at ground at theupper,- niost armature and back contact of `the relay 14.

The relay 7 is operated in this circuit to attract its armature andthrough its inner armature and contact 15, it applies a guard ing'potential to the test terminal 13 of Athe trunk that has` just beenseized and also closes a circuit from ground through the .known manner.description to outline the operation ot'tliese armature :of relay 7 andits contact 15, test terminal 13, test brush 5, inner lower arniatureand front contact of the cut-oitq relay 3 its lower winding to groundedbattery. Under the control of this last described circuit the cuteirela-y is held operated during the period that the connection is mainutained..

lVith the relay 7 operated a circuit is closed forthe motor magnet 16 ofthe secondary line switch Which is now associated with the calling line.This circuit is traceable iirom grounded ybatt-ery Winding ot the motormagnet 1'6, its back Contact and armature, outer armature and frontContact ot the lline relay 7, 'lower back contact and arn-iaturc ot'relay 14, test brush 17, and test terminal such as 18 of busy trunks.rl-his busy condition, as in the previous instance., Ais indicated bythe presence ot ground. 'potential on the test terminals of busy Vtrunkcircuits. Y Let it be assumed that the first idle; trunk circuit testedby the test brush 17' is that indicated in Figure 1, and when this test`takes place the relay 14 which has been shortcircuited, by groundapplied through the test terminal 18 and test brush 17 is now operatedin a circuit completed from grounded battery, 'Winding o" the motormagnet 16 its armature, and back contact Winding of the relay 14:, frontcontact 19 and armature of: the relay 7. to ground; The motor magnet 16is not operated in this last `described circuit, but the relay 111 isoperated to attract its armatures and thereby interrupts the operatingcircuit oi. the slow releasing relay 7 and also functions 4to furtherextend the calling line to the brushes 24 and 25 of the selectedsecondary line switch and through the terminals ot the selected trunkYto an impulse relay such as 22 associated with the numerical switcliofthe trunk just seized.' fFlic impulse relay 22 of this last inen lsuitch Will be operated over the ':ircuit indicated to attract itsarmature and close a circuit 'for actuating the slou' vi'1 relay. 23.This relay when operati .E apply aglioldiiig ground and guar-fling potential-tothe test terminal 1S hy Which the relay 1l will new be lockedoperatedin a circuit extending from grounded battery windingA oi themotor inagnet`16, its back contact, and armature, Winding oi the relay14k louer front contact and armature of this relayY through the -testbrush 17 and the test termina-l. 18 to ground as mentioned.

rlhe .calling subscriber at il. will now operate his dial to/transmitseries ot impulses to actuate, the numerical switches such as theconnector herein indicated to causethese switches to extend theconnection to la called telephone line in the well It is Ynot necessaryin this lif) lli

' relay terasse;

called line is testedand if found idle sig nailed. This portion of thesystem may operate in the manner disclosed in the men-.

tioned Lamb patent.y A

It will be noted that when Vthe primary line switch seizes the secondaryline switch the brushes otl which-are indicated at 17, 24 and 25,brushes 11 and 12 of the primary line switch extend the line whosesub-station is indicated at D, to the secondary line switcn indicated atthe lower portion otFigure 1 Thus whenever the subscriber at A. or D.

initiates a call, the non-numerical vswitch individual to these twolines, extends them to idle secondary line switches.

Let it now be assumed that, after the calling line kwhose sub-station isindicated at A. has been extended through an idle secondary line switchto an idle numerical switch, the

subscriber at D. now initiates a call. At the time when the receiver isremoved from the switch hook at the sub-station at D the line relay 26is energized over the two sidesA of the calling line in series in themanner that has been previously described in connection with the callingline A. Y lVith the line 26 energized ja lbrealr point, in the operatingcircuit of the motor magnet 4 lis closed but since the test brush 10 isnow in engagement with the test terminal 4270i? a trunk leading to anidle sec-- ondary line switch, the motor magnet 4 will not be operatedbut the cut-oit relay 28 will be energized in a circuit from groundedbattery winding of the motor magnet 4, inner armature and front contactof line relay 26 lower winding of the cut-oil' relay 28 to ground. Thecut-oill rel-ay 28 when thus energized attracts its armatures andthereby opens the energizing circuit of the line relay 2G and extendsthe calling line D. to the brushes 11 and 12 of the primary lineswitchand thence through these brushes to the selected trunk leading tothe idle secondary line switch. The extension of this circuit completesan energizing circuit for the relay 29 which attracts its armatures andcloses a holding circuit for the cutsoi relay 28. This circuit istraceable from grounded battery upper winding of this relay, its

,tront contact and armature through the test brush 10,-test terminal27,' contact 30 and armature of the relay 29 to ground. Under thecontrol of this circuit, the cut-oli relay 23 is maintained operatedduring the connection. lVith relay 29 actuated a circuit completed forthe motor magnet 31 of the secondary line switch closed from groundedbattery winding of this motor magnet, its back contact and armatureouter armature and front Contact of they slow releasing relay '29,-upper back contact and armature of relay 32 ,test brush 33 of thesecondary line switch and` throughtest terminals such as 34 to ground atengaged trunk circuits leading to numerical switches.- Under the controlof" this circuitthemotor magnet- 31 `advances the brushes 33. 35 and 36ofthe secondary line switch until an idle trunk is located which will beindicated l by the absence or' ground potential on its test terminal 34.`When such a trunk is located, the relay 32 will bev operated in acircuit extending from grounded battery winding of the motor magnet 31,its back Contact and armature, winding of the relay 32, front contact 37and armature ot relay 29 to ground. It will benoted that previous to the`.location of this idle trunk the relay 32 wasr short. circuited byground on the test terminals ofbusy trunks so that it remained inactive.At this time, however, the relayr 32 is operated and extends the primarytrunk circuit to the seized secondary trunk circuit at which time animpulse relay similar to 22 is energized and this in turn actuates aslow releasing relay similar to 23 which applies ground potential to theholding trunk. The

closure o1 this holding circuit locks the relay 32'in its actuatedcondition. The op- .erating of relay 32 ofcourse interrupts theenergizing circuit of the relay 29 causing this relay to deenergize andremove the holding ground Ywhichhas been applied to the test terminal27, but at this time a substitute holding ground is applied to the testterminal 27 through the test vbrush 33 and the test terminal such as 34of the trunk that has been seized. j y

The apparatus and circuits are now in con; dition to,V receive theimpulses :trom the dial of the calling. sub-station at D. Vand in response to these impulses numerical switches are operated in the wellknown `manner to extend the calling line to the wanted station. Thetesting and the release voperations at these numerical switches willtake place in the manner now well known.

At the termination` of the conversation when the calling subscriber at,station A. replaces his receiver on its switch hook the impulse relay 22of the iinal numerical switch will deenergize and shortly afterwardsthis will eiect the deenergization of the slow` releasing relay 23. Thisrelay, when it retracts its armature removes the holding ground whichhas been applied toA the test terminal 18 as a result oit which therelay 14 andfcut-etia relay will: cle-energize this system are ot thestay-put type they will remain in rengagement with the trunk circuitslast used. The apparatus is now in condition to care for succeedingcalls.

Let it be supposed that it is desired to call and since thenon-numerical lswitches of' station A. f Then'a connectorswitch such'asf (lll wanted line is engaged as a calling line, ground `potential `isapplied through the innermost iront contact and armature .oit thecut-eti rrelay 3 and test brush 5. It this line is idle it willbe seizedand the .cut-ofi relay energized i-n a circuit including its lowerwinding and conductor 42. at this time the line relay 2 has not beenyoperated. so that its arma-ture will prevent the 4complete yattractionof the armatures of cut-oil' relay and thus only its contacts c -areopened.

liet it -be assumed that when the subscriber substation A; initiates acall, :the trunk terminating in the secondary line switch brushes 35 and36 Ilias been seized by another telephone line terminating at asubstation similar to D. Under thiscondition when the test brush 5engages the Atest terminal 13 corresponding to the pair trunksterminating in secondary line switch brushes 24e, 25, and .36, the lineswitch of Fig. l is prevented from seizing this vpair of trunks one ofwhich has .already been seized. The guarding condition on test terminal@Bis afp )lied as .ollowsL-Since it is assumed lthat the klinecorresponding to that rterminating at substation D has seizeda trunkwhile the line .corresponding :to that terminating `in substation A isidle, then ground is applied through 'fthe upper armature .and frontcontact ota relay similaivto 28, outer varmature and back contact of arelay similar yto 2` inner, lower .back Contact and armature of a relaysiinilarto 8 and throughaftestbrush similar to 5 at the primary line:switch which has seized one of this pair otrtrunks to -test terminal13. In this manner the primary line switch of Fig. l is :preventedfromseizing a vpair of trunks one of whichwhas already been seized.

Figure 2 shows the same :principle applied to the distributionfof.callsfrom the incoming trunks to the other trunk circuits. In tl 'sarrangement `the vincoming `trunks may terminate atl distantlautomaticotlice or may terminateiat-jacks-in'operators positionsatidistantolices. In thisarrangement two incoming trunks terminate inthe brushes of a primar y line switch :and this switch functions as soonas one of these incoming trunks is seized to select an idle secondaryline switch.

At ,is believed that the operation of the systemdisclosed-in Figure 2will ,best be understood by describing the method oit extending anincoming trunkcircuit to a wanted station, such as that indicatedat SELet it be assumedthat acallingiline `(not shown) has been extended,Veither.manually or automatically to the incoming trunkcircuit whoseconductors are designated bythe numeral 50. As soon asthis portion oftheconnection has been extended a circuit is completed for theslowrelease'relay 51 eX- tending from grounded battery,A its lupper tactand armature of the relay 52 test brush 55 of the primary line switchand test term,-

inal 56 which iscommon to a pair of trunk circuits leading to secondaryline switches and thence to ground as will be described. t will bepointedout further in .this de scription that lwhenever a trunk circuitis' seized, a .relay such as 571er 5S is energized to apply groundpotential to its terminal, such as 56 individual to this pair `of trunkcircuits.

liet it be assumed :that :the ,rst pair ot idle trunks tested by theprimaryline switch are those shown in Figure 2. As a result ot this'idlecondition, guarding potential will be absent from the test terminal 55.As aresult of which the operating circuit ot the notor magnet 5d isincomplete and this magnet will stop the'brushes o'ithe switchinengagement with Ythe terminals of the ,pairof trunks here shown. e

At this ytime the relay 52 vwhich has vbeen short circuit-ed is nowoperatedin acircuit completed Afrom ground, upper `winding oit' therelay 52, Contact 53 and armature of relay 51; back Contact armature andwinding of the motor magnet 5l to grounded battery.

r he relay 52 is operated in this circuit but themarginal motor magnetwill not be energized in series with this last named relay. As soon astherelay is operated it interruptsthe operating circuit oi the slowreleasing relay 5l but this .relay remains eneroizedjtora short periodto :maintain the original operating circuit of the relay 52. At the`upper armatures and :trent contacts ot' the relay 52, a circuit iscompleted through the brushes :3Q-and (S0 ot the primary line switch andthrough the upper armatures .and back contacts of .the relay 6l toground and through vthe winding olf slow releasing relay 57 to vgroundedbattery. 'The :relay is operated in this 'circuit and at its innerarmature and contact 62 it applies ground potential to the test terminal56 of the selected pair of trunks to prevent Athem from being yseized bylother primary line switches. Also this ground potential is extendedthrough thetest brush 55 .and the innermost armature r,and front Contactoi relay 52, vlower winding of this y 'mature and 'front Contact or'relay 57, Contact G4 and armatuure of relay 61, test brush (55 to ground'at test terminals, such as 66fof busy trunks terminating at thesecondary It will be noted'at` thistime line switch. thatthe relay Glfisshort circuited by this lastdescribed circuit. The moto'r'magnet,however, is operated and advances its-brushes G5, 67, 68 and 69 untilthe vtest brush 65 engages a test terminallGG characterized by theabsence of potent-iai which condition indicates that this trunkis-fidle. "When such an idle trunk is reached the operating circuitA otthe motor magnet 63 is no longer completed and the short circuitaboutjthe relay 6l is no longer 'eli'ective so that this relay is nowenergized in a circuit closed from grounded battery, winding, armatureand back contact ci themagnet 63, winding otl relay (Si, contact andarmature otrelay 57 to ground. Then the relay 61 is thus operated toattract its armatures, thev energizing circuit of the relay 57 isinterrupted and since this relay is slow releasing in itscl'iaracteristics it will remain operated for a short interval tomaintain the energizingcir- V cuit of the relay 6l. At the uppermostvarmatures and front contacts of relay 6l, the connection is furtherextended to the brushes (i7 and 68 and through both windings in seriesot impulserelay 72 associated Vwith the rst numerical switch to groundand battery. This relay is energized vin this circuit and etl'ects theoperation ot vthe slow releasing relay 73 which operates inthe wellknown manner to apply av holding ground `to the trunk' circuit justseized andffurthei' to prevent the release of the selected numericalswitch.

.As soon as the relay 73 is operated,` the` holding circuit for thesecondary line switch is completed from ground at thearmature andt'ront` contact of the relay 73 throughithe test terminal 66 test brush65, innermost lower armature,'front Contact and winding terr.

serves to apply ground potential ,to Vthe test et" relay Gl, ba cont-actarmature and winding ot' the motor magnet 63 to grounded batlt will alsobenot-ed that this circuit terminal 66 to insure that the connectionwill not be disturbed at this point. 'y

"The appara-tus disclosed in Figure 2 is now in condition to bedirectively operatedY in response toV directive impulses transmittedfrom the distant office over the incoming circuit. In response to theseimpulses the nguineric'al 'switches such as selectors and con.1v

nectors will be diiectively operated to extend the connection to thewanted telephonelline, nthe sub-stationy of whichis indicated at E. Thearrangement and operation of these numerical switches may be similart'othat disclosed in the'mentioned patent to Lamb, and

`for this reason it is not-necessary to describe 'the operation or lthemanner inA which` the wantedline is tested and= if idle, signalled;`Itis sutiicicnt to state that at the termination of Ythe conversationwhen the incoming trunltcircuit is opened either by the removal of theoperators calling plug at the distant office (not shown) 'in the manualsystem or by the operationof the repeater (not shon n) ina fullautomaticsystem, relays such as 72 and 73 associated with theiinal numericalswitch are released toremove ythe holding.

ground from t-he te-st terminal 66 so that the relay 61 willcle-energize. Similarly vthe holding circuit of the relay 52 which wasextended through the test terminal 56 is f also opened sothatthe relay52 also de-energizes. Since thek primary line switches and-the secondaryline switches in this arrangement are also of the stay-put type, theyremain in engagement with the trunks last used. Y Y

It will thus be seen-that whenever a, call isk extended over theincoming trunk circuit 50 or the `incoming trunk circuit 71k the primaryline switch individual to these two trunlrcircuits vis operatedA toextend these circuits to anidle pair of trunlrc'irc-uits leading ytosecondary line switches. f

It' the call originates over the incoming trunk 74 instead of over trunk5,07 the relay 5l is energized in a circuit completed through its lowerwinding and over both sides of the incoming trunlfcircuit in series toground.k

With relay 51 operated the motor magnet 54 yadvances the brushes of theprimary linev switch as in the manner already-described.

Let it be assumedthat the incoming trunk circuit 50 has been extended tothe secondary line switch shown inthe upper portion `of Figure 2 andthat a call is then extended over the incoming trunk circuit 74. Therelay 5l will not be energized since its operating circuit is open atthe innermost lower contact and armature of relay 52 and therefore themotor magnet 54 will not be actuated so that the primary line switch isnot moved from the pair of trunks already seized. The relay 58 will thenbe operated to close Yan energizing circuit for `the n'iotoimagnet 75 ofthe secondary linefswitch shownin the lower portion of Figure 2. y Thismotor magnet will then begop'erjated in the manner described inconnection with the other secondary line switch of this disclosure toadvance its brushes 76, 77, 78land 79 until its test brush 77encountersv a test yterminal similar to 80,* which is characterized bythe absence oaguarding potential 'at-which time the motor lmagnet 7 5will cease tol operate and over the incomingptrunl; circuit will beineli'ective to disturb the connection over the incoming trunk circuit 71 since the holding circuit for the primary line switch is controlledover parallel holding circuits independently controlled at -thenumerical switches in succession of the extended connections.

` In the event that both the seconda-ry line switches of Figure 2 are inuse simultaneously and it' one ofthese line switches is to be releasedbefore the other, a different releasing arrangement is provided fromthat previously described. It will ben'ot'ed that when the relays (S1and 81 of the secondary line switches of Figure 2 are energized,indicating that these switches are in use, a circuit is completed fromground, at the arma-ture and front contact oit' relay/73, test terminalG6, test brush 65, innermost armature and front contacts of relay 61 andthrough the innermost, upper, front contacts and armature of relay 81,winding of this relay, back contact, armature and'windi'ng of the motormagnet to grounded battery. lt will thus be seen that if `it is desiredto :release the secondary line switch at the lower portion of Figure 2while the relay 01 o't the upper secondary line switch is operated, somemeans must be provided to release the relay S1. This is accomplished inthe following manner. l'Vhen the release magnet R. E. L. associated withone of the numerical switches such as the connector switch, is operated,it completes a circuit from ground, its armature and front contact,Ytest brush 7 6, middle upper armature and front contact of relay 81,`lowerm'ost. front contact and armature of relay 61 winding` of themotor magnet 75 to grounded battery. This last described circuit iseffective to short circuit the relay 81 causing it to deenergize andrelease the secondary line switch. Similarly if the secondary lineswitch at the lower part of Figure 2 is in use 1when it is desired torelease the secondary line switch at the upper portion of this ligure, asimilar circuit/is `completed to the brush 69 of that line switch toeect the deenergization of relay 61,.

ln the modified torni of the invention shown in Figure 3 this principleis applied to a `ful-l automatic system in which one line relay isprovided for each pair ot' telephone lines, likewise also, theinterlocking line and cut ott relaysl such as L. R. and C. O. or' Figure1 have been associated with secondary line switches, so that theirnumberfs greatly reduced. lith this brief outline of the system otFig-ure 34 it is believed Lee-eea 'that the operation of the same willbe best understood by describing the method of establishing a telephoneconnection from the sub-station such as M to a wanted substation such asthat indicated at O. lVhen the subscriber removes his receiver from itsswitch hook a circuit is completed for the line -rela-y 100, extending`from grounded battery upper winding of this relay, innermost backcontact and upper armature ot the cut ott relay 101, over the lower sideof the calling line, and through the sub-station circuits i'n series andover the upper side of the calling line to ground at the uppermostarmature a-nd back Contact of the' cut-oil relay. The line `relay isthus energized and at its lower armature and front contact closes abreak-point i-n the operating circuit oi' the nrotor magnet 109. ,In theevent that the brushes of the 'line switch are fin enga-gement with busytrunk circuits the test brush 10313 ot the line switch will be inengagement with the test terminal such as 10% com-mon to a pai-r ot'trunkcircuits which is characterized 'by the presence of groundpotential. lVhen the line relay is thus energized to close lthementioned break point and with the test brush 103' in engagement wi-th abusy test terminal, an operating circuit is closed for the motor magnet102 from grounded battery winding of this magnet, its back contact andarmature, lower armature and front contact of the line relay 100lowermost back contact and armature oit the cut-olf relay 101, testbrush 103, test terminal 104 toA ground, at the front contacts andarmatures of some one of the relays 105, 106, 107 or 108. Under thecontrol of this circuit the motor magnet 102 advances its brushes 109,110, 111, 103, 112, 113 and 1 1-l until the test brush 103 encounters atest terminal, 10st which is characterized by the absence of groundpotential indicating that its associated trunks are idle. Then such testterminal is reached the operating circuit of the motor magnet 102 willno longer be completed and the primary line switch will be stopped withits brushes in engagen'ient with the selected trunk circuits. At thistime a circuit is completed from grounded battery winding of the motormagnet 102 its back contact and armature, winding ol' the cut off relay101, upper front contact and armature or the line relay 100 to ground.Thecut offyrelay is energized in this circuit and at its upper armaturesand back contacts it interrupts the operating circuit oi` the line relay100, but this relay is of the slow rcleasing type and therefore holdsits armatures operated for a relatively short interval to maintain theinitial energizing circuit of the cut ott1 relay 101. At the uppermostarmatures and Jfront contacts of the cut oit' relay,the conductors ofthe calling nline are extended to the brushes 109 and 1,210 of vtheprimary line switch and through the terminals with which these brushesare in engagement to the two sides of the selected trunk and thence toground at the uppermost armature and back contact of relay 105` anol togrounded battery through` the inner upper armature and back contact ofrelay 105 and the winding of slow releasing relay 106. The relay 106 isenergized-in this circuit to attract its armatures and at its innerarma-k ture and contactfllv it closes a holding circuit for the primaryline switchextending from ground through lcontact 104, test wiper 103,lower armature and front Contact of the cut oli relay 101, winding ofthis relay, arma* ture, back contact and winding of the motor n'iagnet102` to grounded battery. rfhe closing of thel inner arn'iature andcontact 116 of relay 106 applies a guarding potential to the line switchbrush 111 and through the front contact and inner lower` armatureof thecut off relay 101 to the conductor 117 leading to the multiplecontactsof the calling line at the various connector switches throughwhich it may be reached as a called line. At the outer' armature andfront contact of relay 106 a break point is closed in the operatingcircuit of the motor magnet 118 of the se'- lected line switch and inthe event lthat the brushes 119, 120, and 121 of this line switch are inengagement with a busy ktrunk leading to an engaged numerical switch thetest terminal such as 122 of this trunk will be characterized by thepresence of ground potential applied from the armature and front;

Contact of a relay similar to 123 at some one of the numerical switchesin the connection. As long as thetest brush 121 is testing busy trunksan operating circuit is closed for the motor kmagnet y118 from groundedbattery winding of this magnet, lits backcontact and armature, outerarmature and front contact of relay 106, back contact anda-rmature ofrelay 105, test bruslr121 and test terminal such as 122 of the busytrunk to ground at the trout contact and armature of arelay similar to123. yUnder the control oi. such operating circuits the motor magnet 11Sadvances its brushes 119, 120 and 121 of the secondary line switch untilan idle trunk is located. .p

Let is he assumed that .the iirst idle secondary trunk tested is thatappearing in Figure 3, under which assumption when the test brush 121enga ges the test terminalv122 due tov the absence of the vgroundpotential on test terminal 122 the operating. circuit of they motormagnet 118 will no longer Vbecompleted so that it will stop the lineswitch lwith its brushes in engagement with this selected trunk.

It will be noted that as soon as the relay 106 is actuated a circuit isclosed from grounded battery through the vwinding ot' the motor magnet118, its baclficontact and armature, [winding of the relay 105, kfrontcontact 1116 and k'armature of relay 106 to ground, but this lastdescribed circuit Lis ineffective to operate relay 105 because of theshort circuit completed Athrough the test j matures attracted for akrelatively short interval after its operating circuit kis broken. At theuppermost armatures and front contactsof vrelay 105 ythe connection fromthe calling line previously established, is now extended through thesecondary line switch brushes`119 and 120, over. the two sides of theselected trunk and the winding-of the impulserelay such as 124 of thesucceeding numerical switch to ground and battery. Relay `124e is.energized in this circuit and eliects the operation ot slow releasingrelay 123 which attracts its armature to apply ground potential to thetest terminal 122y of the selected trunk and also completes a holdingcircuit through its brush 121, inner lower armature and front contact ofrelay 105 winding of relay 105 armature back contact and winding of themotor magnet 118 to grounded battery. n

It will be noted that the holding circuit for the primary line switch isnow completed to ground through the front contact a`ndar mature. of the,relay 105. rThe ap paratus is now in condition to receive di* rectiveimpulses from the dial sender at the calling substation ybut it is notnecessary to describe the operation of `the numerical switchessuch'asthe connector herein shown to establish the wanted connection,since suchoperation isnow ywell known in the art and' may be similar tothat outlined in the mentioned patent ,to Lamb. n

ALetkit be assumed that` the ,subscriber at substation N. desires toestablish a telephone connection d-uring the time that subst-ation M iscalling; Y v Y Under the conditions assumed t-he `cutoff relay 126- otthe calling line N is in operatedrondition `since it kwas' energized inmultiple with the cut Off relay 101, as soon as that relay was;operated. Also the brushes 113 and-114 of the primary line switch willbe in engagement with -the terminals of the selected primary trunkssince the prei-iously -mentioned operation of the primaryfline switchYwas effective to select a pair of idle trunks. lVhen the subscriber at NIremoves his receiver from its switch hook the slow releasing relay 107of ythe secondary Alineswitch will be immediately energized in a'eircuitclosedfrom grounded il U ino

` of' the, secondary' battery, winding ofthis relay, inner lowerarmature and back contact of rela-y 108 and through the tivo lines ot"the selected primary trunk and calling line in series to ground at theloivermost armature `and back contact oit relayv 108. Relay 107 at itsinner armature and contact 128 applies a guarding potential through4terminal 127, brush 112 upper front contact and armature ol the cut olirela-yr 126 through the multiplev tern'iinals (not slroyvn) et the'calling' line at a' group of vconnector svvitches, Also at this Atimethe motor magnet 132 ine switch is operated in circuit completed fromgrounded battery, Winding ol' the motor magnet 132, its back contact andarmature, outer armature and trent ctnitact ol' relay 107, inner upperback con-tact and armature ol relay 108,' test brush 12.9: and testterminals such as 133 ot busy trunks to ground at 'the liront Contact'and armature' of a relay such as y123 at' the succeeding numericalswitch. When such tan idle secondary triink is located it will becharacterized by the ab-y sence ot 'ground potential at itsftes'tterminal and the voperating circuit vof the Minotor n iagnet 132 rvillno longer be complete so that the 'secondary line s ivitch will stop itsbrushes 1219, 130 and 131 in engagement with the` terminals 'of an idlesecondary trunk. rlhe relay 108 which 'has been short circuited duringthe operation of the secondary line switch is now energized fromgrounded batteryI Winding ol the motor magnet 132 its 'back contact andarmature ivindinjg of relay `108 contacty12`8 'and armature of relay 107to ground. As soo'n as the relay 108 is energized in this circuit it islocked operated through its innermost upper front contact and armature,test brush 129 'and test terminal similar to 133 to -grour'id at thefront Contact and 'armature of the relay similar ui 123 at the selectednumerical switch. i l A lVhen a calling subscriber such as M deci des toterminate the connection, he replaces his receiver on its switch hook atwhich time a relay such as 124 of the inal numerical lsivitch has itsoperating circuit interrupted and d'e'e'nergizes to effect the releasevol a relay such as 123 which has been holding the connection. The relay123 on dcenergization removes the holding ground from the test terminalsuch as 122 which caiises the relay 105 of the secondary lin-e Sisyphetyp their hashes ieii'iaih `iiieii-gageinent With the terminals ot thetrunks last used.

Let it be assumed that it is desired to call the line terminating atsubstation M. lVhen a connector switch (not shown) seizes this line,ground at the connector Will be applied to the conductor 117 s'o that acircuit is coinpleted through the louer Winding of the line relay 100 togrounded battery. The line relay 100 is energized in this circuit and ifthe tivo sets of brushes or' the primary line siv'itch are inei'i'gag'ement with busy trunk terminals the motor magnet 102 willadvance the brushes of the primary line switch until idle tru-nhs' arelocated by the test brush 103 'at ivhi'ch time the cut olf rel-ay 101 ofthe called line Will be operated in the manner already described. Assoon as the contacts of relay 101aie thus operated the test con-- ductor117 is extended through its inner loi'ver armature and front Contact,line sivitch brush 111, ivindin'g of relay 105, armature, back Contactand winding of the niotor magnet 118 to grounded battery, and since therelay 106 has not been operated prior to the operation of relay 105,this last named relay although energized will operate all its contactsexcept these marked c. It Will thus be seen that the relay 106 will notbe operated when the called party removes his receiver from its switchhook and likewise the brushes 119A and 120 ot the secondary lines'ivitclr are not connected to the called line. The cut oil relay 101,however, is locked operated through the test brush 103 to ground at theloiif'ermost front contact vand armature of relay 105'.

Atthe termination of the Vcall to the line M. when the callingsubscriber releases the connector, ground potential will be removed fromconductor 117 so that the relay 105 Will release and at its lowermostarmature and trontcontac't open the' holding circuit of the cut oitrelay 101.

It irill be understood that the arrangements disclosed in thisapplication are merely typical of applicants invention and the saine maybe Widely varied Within the scope of the appended claims Withoutdeparting 'from the spirit ot the present invention.

that is claimed is z- 1. In a Atelephone system, an automatic sivi't'chprovided with sets ot brushes and fixed terminals, a pluralityotindependent incoming circuits, one incoming` circuitterminating iii eachset ot brushes, a plurality ottrunks t'eijiiiinating in said lixedterminals, means for rendering` trunks busy, and means l'or operating `aswitch to extend its incoming circuits to idle trunk Acircuits inresponse to the initation ot a call oiier one ofmsaifdincoiningcircuits.

e. 'The method of extending @ii-cuits which consists in arrangingcircuits into groups a call over either of said incoming circuits 65 andsub-groups, arranging trunks groups, extending all the circuits of asuhgroup to seize idle trunks ot a group on the initation of a call overone ot said circuitseral incoming circuits and trunk circuits ter-k cminate, means controlled over the two sides et an incoming'circuit inseries 'for operating said trunk limiting switch to Ventend the incomingcircuits to idle trunk circuits, and means to extend said last mentionedtrunks separately and conteinporaneously.

5. In a telephone system, a plurality ot independent incoming circuits,a plurality of trunk circuits, means including primary and secondaryline switches for interconnecting incoming circuits and trunk circuits,each primary line switch heing connected to a group otincoming circuits,and means responsive to the initiation 0i a call over any ci saidincoming circuits of a group for extending all of the incoming circuitsof this group to idle secondary line switches.

G. In a telephone system, a plurality of independent incoming circuits,a plurality oi out vgoing circuits, a trunk-hunting nonnumerical switchin which said incoming circuits terminate and means including saidnon-numerical switch responsive to a call over any of' said incomingcircuits for extending all of said incoming circuits to idle outgoingcircuits.

7. In a. telephone system, a non-numerical switch provided with brushesand iiXed terminals, a pair oi incoming circuits terminating in saidbrushes, trunk circuits terminating in said lined terminals, meansresponsive to the initiation of a call over either ci said pair ofincoming circuits for operating said switch, a single test brush forsaid switch, and means controlled through the same tor stopping saidswitch in engagement with idle trunks.

8. In a telephone system, a pair oi incoming circuits, a plurality oittrunk circuits, a non-numerical switch individual to said pair otincoming circuits, means for advancing said switch on the initiation ofinto circuits.

busy,

-ior extending the saine to idle trunk circuits, and holding circuits'for said switch controlled at any one of said selected trunk 9. In atelephone system, a plurality oft incoming circuits, a pluralityooutgoing circuits, a nonaiumerical'lswitch in which said incomingcircuits terminate, said nonnumericalswitch 'functioning to` extend said`icomiiig circuits to idle outgoing circuits, a motor magnet forcontrolling the i-arious Loperations ot said noirnunierical switch, arelay controlled over any oi' said incoming circuits ttor initiating theoperation of said meter magnet, and a relay controlledover any oi saidoutgoing circuits and held operated during a connection for disconnecting said first relay from control of said incoming circuits.

10. In a telephone system, ank automatic switch provided withV sets otbrushes and passive terminals, a plurality of primary circuits, aprimary circuitterminating in each set of said brushes, a plurality ofsecondary circuit terminating in said passive terminals, means `forrendering saidcircuits and means for operating a switch to extend itsprimary circuits to idle secondary kcircuits when a call is initiatedover one ot said circuits.

l1. In a telephone system, a plurality oi incoming circuits, a pluralityof outgoing circuits, a non-numerical switch in which several incomingcircuits and several outgoing circuits terminate, and meansincluding arelay contrellahle'over th-e two sides of any one of a plurality of saidincoming circuits in series ior operating said nonnumerical switch toextend each of its incoming circuits to a separate idle outgoing icircui ,12. In a telephone system, a pluralityr oi'1 rincoming circuits,a plurality of outgoing circuits, 'a non-numerical switch in whichseveral incoming` circuits and several outgoing circuits terminate,means including.

a relay controllable over the two sides ot any one of a plurality or"said incoming circuit in series, and a motor magnet governed by saidrelay for operating said non-numerical switch to extend each ot itsincoming circuits to a separate idle outgoing circuit.

13. In a telephone system, a plurality oi incoming circuits, a pluralityof outgoing circuits, a non-numerical switch in which several incomingcircuits and several outgoing circuits terminate, means including arelay controllable over the two sides of any one of a plurality of saidincoming circuits in series, a motor magnet governed by said relay foroperating said non-numerical switch to yextendr all ot its incomingcircuits, to idle outgoing circuits and a cut-oil' relay operatedresponsive to the extension of said incoming circuits to disable saidiirst relay.

14. In a telephone system, a plurality of independent incoming circuits,a plurality of trunk circuits, means including primary and secondaryline switches vfor interconnecting incoming circuits and trunk circuits,said primary and said secondary line switches being of the type thatremain in the position last used, each primary line switch beingconnected to a group of incoming circuits, and means responsive to theinitiation of a call over any of said incoming circuits of a group forextending all of the incoming circuits of this group to idle secondaryline switches.

15. In a telephone system, a primary line switch having two sets ofbrushes and sets of fixed terminals, a telephone line terminating ineach of said sets of brushes, a plurality of trunks each terminating atone end in a set of tiXed terminals, a secondary line switch for theother end of each trunk, means for seizing one of said telephone linesas a called line, means responsive to such seizure for extending saidcalled telephone lines to a secondary line switch, and a trunk releasearrangement for controlling the release of operated switches.

In witness whereof, I hereunto suhscribe my name this 5th day of May A.D.

WINFRED T. POWELL.

